It is my opinion that the use of longer ropes adds to the chance of more accidents. The most common one I believe is that unaware climbers rap off the end of their rope. Second, it puts the belayer and climber further apart making it hard to keep eye contact with each other which can be important. Third, with that much rope out there is a lot of stretch and if the second climber falls near the deck no matter how tight the leader is belaying the second will hit, sometimes with considerable force. I'm not saying that the longer ropes shouldn't be used just that there are some things to be considered. On a positive note just think how a longer rope helps the economy as we have to spend more $$$ per rope. I seldom see anyone buying a 50 meter rope anymore and with the popularity of 70 meter ropes just starting the 60 may be on the way out as well.